The specific role of isoflavones in reducing prostate cancer risk

Kumar, Nagi B.; Cantor, Alan; Allen, Kathy; Riccardi, Diane; Besterman-Dahan, Karen; Seigne, John D.; Helal, Mohamed; Salup, Raoul; Pow‐Sang, Julio M.

doi:10.1002/pros.10362

Cited by 137 publications

(86 citation statements)

References 15 publications

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“…Previous clinical trials in men with prostate cancer have reported relatively minor side effects of chronic isoflavone treatment including symptoms related to estrogenic effects such as breast changes, lowered libido, and increased frequency of hot flashes (2). Unlike earlier reports, no symptoms related to estrogenic effects at this dose and period of intervention were observed.…”

Section: Resultscontrasting

confidence: 72%

“…The initiation and progression of prostate cancer is a multistep process including several intermediate steps and may involve a complex series of both exogenous and endogenous factors (2)(3)(4)(5). Although it is clear that clinical prostate cancer incidence and mortality vary greatly between populations, the frequency of latent prostate cancer is evenly distributed among populations, suggesting that external factors such as diet and other lifestyle factors are important in the transformation from latent into more aggressive, clinical cancer (4)(5)(6).…”

Section: Introductionmentioning

confidence: 99%

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A Phase II Randomized, Placebo-Controlled Clinical Trial of Purified Isoflavones in Modulating Steroid Hormones in Men Diagnosed With Localized Prostate Cancer

Kumar

Krischer

Allen

et al. 2007

Nutrition and Cancer

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Our purpose was to evaluate the safety and effectiveness of purified isoflavones in producing an increase in plasma isoflavones and a corresponding change in serum sex hormone binding globulin (SHBG) and steroid hormone levels in men diagnosed with early stage prostate cancer. In this Phase II randomized, double-blinded, placebo-controlled trial, 53 prostate cancer patients with a Gleason score of 6 or below were supplemented with 80 mg purified isoflavones or placebo for 12 weeks. Changes in plasma isoflavones, serum steroid hormones, and safety markers were analyzed from baseline to 12 wk. A total of 50 subjects completed the study. Although significant increases in plasma isoflavones (P < 0.001) was observed with no clinical toxicity, the corresponding modulation of serum SHBG, total estradiol, and testosterone in the isoflavone-treated group compared to men receiving placebo was nonsignificant. Increasing plasma isoflavones failed to produce a corresponding modulation of serum steroid hormone levels in men with localized prostate cancer. The study establishes the need to explore other potential mechanisms by which prolonged and consistent purified isoflavone consumption may modulate prostate cancer risk.

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Section: Resultscontrasting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

A Phase II Randomized, Placebo-Controlled Clinical Trial of Purified Isoflavones in Modulating Steroid Hormones in Men Diagnosed With Localized Prostate Cancer

Kumar

Krischer

Allen

et al. 2007

Nutrition and Cancer

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“…As soy isoflavones have been detected in much higher concentrations in prostatic fluid than in the serum, they may also act locally (Hedlund et al, 2005). The small (14%) decline in mean serum PSA level on the high soy diet is consistent with an intervention using a soy protein supplement among prostate cancer patients that showed nonsignificant declines in serum PSA and free testosterone in the soy isoflavone supplemented group (Kumar et al, 2004). PSA is thought to be an indicator of cell proliferation and commonly used during prostate cancer risk screening.…”

Section: Discussionmentioning

confidence: 55%

Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men

et al. 2006

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Background: Low prostate cancer incidence and high soy intake in Asian countries suggest a possible protective effect of soy foods against prostate cancer. The goal of this pilot study was to evaluate the feasibility of a randomized, crossover soy trial among men and to investigate the effects of daily soy intake on serum prostate-specific antigen (PSA) and testosterone levels. Methods: We randomized 24 men to a high or a low soy diet for 3 months. After a 1-month washout period, the men crossed over to the other treatment. During the high soy diet, the men consumed two daily soy servings; during the low soy diet, they maintained their usual diet. During the entire study each man donated four blood samples and five overnight urine samples. Dietary compliance was assessed by soy calendars, 24-h dietary recalls, and urinary isoflavone excretion measured by highpressure liquid chromatography with photodiode array detection. Blood samples were analyzed for serum testosterone and PSA by radioimmunoassay. When necessary, variables were log transformed. Two sample t-tests compared the two groups before each study period. Mixed models incorporating the repeated measurements were used to evaluate the effect of the soy diet on urinary isoflavone excretion and serum analytes. Results: Twenty-three men aged 58.777.2 years completed the study. The compliance with the study regimen was high according to self-reported soy food intake and urinary isoflavone excretion. No significant between-group and within-group differences were detected. During the high soy diet, dietary isoflavone intake and urinary isoflavone excretion increased significantly as compared to the low soy diet. A 14% decline in serum PSA levels (P ¼ 0.10), but no change in testosterone (P ¼ 0.70), was observed during the high soy diet in contrast to the low soy diet. Conclusion: The high adherence as shown by three measures of compliance in this pilot trial demonstrated the feasibility of an intervention based on soy foods among free-living men.

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“…One randomized, placebocontrolled trial of 12 weeks treatment with genistein in men with early prostate cancer found no significant difference in PSA levels between the treatment and placebo groups (Kumar et al, 2004), although the authors suggested that surrogate measures were being affected by treatment. Other trials support the idea that isoflavones, even given over relatively short periods of time, can possibly slow the rate of rise of PSA, though no statistically significant conclusions can be drawn (Dalais et al, 2004;Hussain et al, 2003;Maskarinec et al, 2006;Pendleton et al, 2008 (Davis et al, 2000;Takahashi et al, 2006;Tepper et al, 2007) b. c. d. (Nakamura et al, 2002;Tsui et al, 2008 (Davis et al, 1998) b.…”

Section: Clinical Studies In Prostate Cancermentioning

confidence: 99%